The present invention relates to the production of coke preferably for metallurgical use by way of oxygen-alkylation of coal.
In general, the better the caking properties of coal, the more suitable it is for metallurgical coke formation. For various reasons, coals characterized by moderately, weakly and non-caking qualities are used in metallurgical coke formation after their caking properties have been improved. Caking properties of such coals are usually improved by physically mixing or blending them with a binder material prior to pyrolysis. This binder material helps to agglomerate the coal into a molten plastic or liquid state when it is heated to pyrolysis temperatures. Subsequently, when the coke is cooled, a coherent solid is formed characterized by an isotropic appearance and a hardness which is suitable for metallurgical purposes. Examples of binders which have been employed for increasing the caking properties of coal include coal-derived and petroleum-derived carbonaceous materials such as coal extracts, tar, pitch, tar oil, fuel oil, asphalt, crude petroleum extracts, bitumen, and the like. However, the use of such binders may not be economically attractive because relatively large amounts of such binder material are usually required in order to significantly increase the caking properties of a moderately weakly or non-caking coal.
Furthermore, coal liquids and gases derived from pyrolysis of coal generally evidence undesirable properties. For example, coal liquids are generally found to be relatively unstable and have a tendency to polymerize in a matter of days; thereby forming highly viscous liquids and eventually solid tars. Coal gases usually evidence relatively low heat values.